Incandescent light bulbs are seldom used in commercial lighting applications because about 95% of the input energy generates heat, not light. Commercial fluorescent fixtures have replaced incandescent fixtures in offices because fluorescent fixtures, such as troffers and surface boxes, are more cost efficient and provide exceptional light. The most common fluorescent fixtures used today are lay-in-troffers, usually 2xc3x974 foot, which lay into a suspended ceiling. There is nothing particularly wrong with the troffers, but the fluorescent lamps, most commonly 4 foot T12 or T8 tubes, have many drawbacks that are considered acceptable because there have been no alternatives that are cost-effective.
Fluorescent lamps are long tubes that contain mercury and argon gas. Electrodes sealed into each end of a tube allow the lamp to conduct an electric current, thereby emitting ultra-violet radiation. The tube of a fluorescent lamp is a glass envelope. The inside surface of the tube is coated with a phosphor that provides visible illumination when excited by ultra-violet radiation. The phosphor, or fluorescent coating, may be harmful to a person""s eyes. The glass envelope is infamous for its ability to shatter and blanket an area with sharp glass. The neurological toxicities associated with mercury exposure are well documented. Additionally, only a portion of the radiation produced by a fluorescent lamp is ever converted into visible light. As with incandescent light bulbs, the excess radiation produces heat. Collectively, the heat generated by these lamps places a tremendous burden on the air conditioning system of a building, especially during the summer months in warmer climates. There is a need for a more energy efficient luminaire that does not include all of the hazards of fluorescent lamps.
The benefits of what are commonly referred to as white LEDs are becoming increasingly known. Some examples of white LEDs are shown and described in U.S. Pat. Nos. 6,163,038 and 6,303,404, incorporated herein by reference but not limitation. White LEDs are much more energy efficient than fluorescent lamps, do not generate very much heat, and provide illumination that presents colors more closely to the way they look in natural sunlight. Additionally, white LED light tends to increase scotopic sensitivity, thereby increasing the perceived brightness of a room without producing an uncomfortable work environment.
The present invention is a method for converting fluorescent luminaires into LED luminaires. The method will retrofit a commercial fluorescent fixture without requiring removal of the fixture housing. First, a fluorescent luminaire is stripped of its lamps, wireway cover, ballast(s) and tombstones. A novel LED retro-reflector is mounted to the fixture housing. LED (Light Emitting Diode) light strips are pre-assembled to a lighted surface of the LED retro-reflector. The LED retro-reflector also conceals an LED power supply that has also been mounted to the fixture housing.
The lighted surface of the LED retro-reflector is preferably a highly reflective white, but some of the more common white LED lamps are designed so that there is little or no need for a separate reflector to redirect light. When such white LED lamps are used, the LED retro-reflector should still be white, but does not necessarily need to be highly reflective. Any existing diffuser or louver that was part of the fluorescent luminaire may be replaced after the LED retrofit has been completed.